Structural toy



Nov. 3, 1959 J. c. A. Ma wLLAN 2,910,737

' STRUCTURAL TOY Filed June 28. 1957 FIG. I.

STRU TOY James C. A. MacMillan, Pittsburgh, Pa.

Application June 28, 1957, Serial No. 668,795

Claims. (Cl. 20-1) The present invention relates to a structuraldome-like toy corprising three dimensionally curved segments and inparticular to a toy igloo and similar structures.

Construction toys generally comprise rectangular configurated blocksfrom which building structures are then produced. However, in thegeneral toy field not much has been done with the construction ofdome-like structures from three dimensionally curved building blocksegments. Apparently the reason for this is because it is difficult toproduce such segments or elements economically which can then be fittedtogether to produce a dome-like structure. Such segments would have tobe curved in three dimensions and would have to be made suliicientlyaccurate so that the parts can be fitted together easily by children.Inaddition, each of the curved segments should be structurally stable soas to enable them to be seated in position one on top of the otherwithout toppling over, particularly near the top of the dome where thereis a substantial overhang of the inner surface due to the internalcurvature of the inner wall of the dome.

It is the object of the present invention to provide a plurality ofthree-dimensionally curved, structurally stable building block segmentsfrom which dome-like toy structures can be produced.

Another object is to provide a toy igloo comprising a plurality offittable, three-dimensional curved building blocks characterized in thatthe curved segments are configurated so that each is structurally stablealone or in combination with each other.

These and other objects will more clearly appear when taken inconjunction with the following description and the accompanying drawingswherein:

Figs. 1 and 2 show the elevation and top views, respectively of anigloo-shaped structure produced from three-dimensionally curvedsegments;

Fig. 3 is a cross-section of the igloo taken along line 3-3 of Fig. 2 asviewed in the direction of the arrows showing three layers of buildingblock segments topped by a spherically shaped cap;

Fig. 4 is similar to Fig. 3 and shows a partial crosssectionillustrating two layers of building block segments similarly topped by acap;

' Fig. 4a shows how the curved building block segments illustrated incross-section in Fig. 4 appear in three dimensions;

Fig. 5 is illustrative of connecting means which may be employed to fitvarious curved segments together in producing a unitary dome; and

Fig. 6 shows how the connecting means illustrated in Fig. 5 can be usedin combination with a cam bolt to effect a rigidly constructed dome. l

Referring to the drawing, Figs. 1 and 2 show one embodiment of a toyigloo produced in accordance with the invention comprising a dome-likeportion referred to generally as it, and an entrance portion 2. Thedomelike portion l is made up of a plurality of three dimennite StatesPatent D sionally curved segments such as segments 3 and 4 which areshown in Fig. 5. The segments are characterized by top and bottomportions 4a and 4b as shown in Fig. 4a. The top and bottom portions arereferred to broadly as fiat supportable surface portions of curvilinearcontour, the fiat surface lying in a plane which passes transverselythrough and, preferably, substantially perpendicular to the polar axisof the dome-like structure produced when the curved segments areassembled together. The curved segmentsare also characterized by flatside portions 40 and 4d as shown in Fig. 4a, the flat side edges alsobeing of curvilinear contour, the fiat side surface lying in radialplanes which preferably contain the polar axis of said dome-likestructure. The polar axis referred to would be the axis A-A as shown inFig. 1 of the dome-like igloo. When the curved segments are configuratedas described above by molding, they. are easily assembled together sideby side and one on top of another to form an accurately assembleddome-like structure. The top of the dome may comprise a cap 5 as shownin Fig. l, or triangular curved segments fitted together to form a cap.

It is important that the three dimensionally curved building blocks bestructurally stable, that is be capable of standing up either alone orone on top of the other without falling over. To achieve this stability,the curved blocks, at least those above the first row forming the baseof the igloo, should be so contigurated in crosssection that the centerof gravity of the block is maintained well within the block itself. Thisessential feature of the invention will more clearly appear from thecrosssection of the igloo shown in Figs. 3 and 4. In Fig. 3, curvedblocks 6, 7, 8, 9, 10, 11, either alone or in cooperative relation, arestable and will maintain the dome shape without falling over. Block 8which has the greatest overhang (note inner curved surface 8b) istapered in cross section (by convergence of curved outer surface So toinner curved surface 8b) so that the center of gravity of the block ismaintained well within its cross section, that is to the left of innerbearing or fulcrum edge 8a of the base of the block. By drawing dot anddash line C-C perpendicular to the base of the block through 8a, it willbe noted by inspection that a substantial portion of the cross-sectionalarea of the block is to the left of this line, thereby insuringstructural stability. Likewise, the three curved blocks 6, 7 and 8,taken together as a unit, must be stable relative to fulcrum edge 6a.Thus, by inspection it will be noted that taking together the totalcross sectional area of blocks 6, 7 and 8, a good portion of this arealies to the left of line BB passing through fulcrum edge 6a. The same istrue of elements 9, 10 and 11. In other words, it is important forstructural stability that the inner and outer curved wall surfaces ofthe dome, such as 12a and 12b, should taper or converge one towards theother so that the center of gravity should be well within the wall massof the block, interior of its inner fulcrum edge. By inner fulcrum edgeis meant such edges as 8a, 6a, etc. about which the block or group ofassembled blocks would topple if the center of gravity of the section isto one side of the edge in the direction of the dome axis.

Fig. 4 is similar to Fig. 3 with the exception that only two horizontalrows of curved blocks are used to form the major portion of the domestructure before topping the two rows with polar cap 5. Thus, it will benoted with respect to block 14 that outer curved surface 14b and innercurved surface 14a substantially converge towards one another. Yet,despite the substantial overhang of curved surface 14a, the block isstructurally stable as shown by the larger amount of cross-sectionalarea to the left of line E--E passing through fulcrum edge 14c.Likewise, the two blocks taken together are sional puzzles.

structurally stable as shown by the amount of cross sectional area tothe left of the line D-D passing through fulcrum edge 13a.

The foregoing feature makes the curved building blocks easilymanipulatable by a child and once the toy dome or igloo is constructedit also retains its structure by the wedging and keying action of theblocks whose sides, eg 40 and 4d, lie in radial planes which preferablycontain the polar axis of the dome. Thus, the blocks need merely bepiled one on top of theother as in Fig. 4a, the shape of the blockdetermining its relative position in the dome.

If a rigid structure is desired capable of withstanding vibrationaldisturbance within its immediate environment, connecting means may beutilized between adjacent coinciding flat surface portions of thesegments. This is illustrated with particularity in Figs. 5 and 6 of thedrawing. Fig. 5 shows a bottom curved segment 4 having a recess which isdirectly below a connecting means or dowel l6 projecting downwardly fromcurved segment 3.

In Fig. 6, a similar structure is shown with the exception that recess15 has a hole passing through it from the outside, the hole lining upwith the hole in dowel 16. The hole has a revolving cam 17 therein withan offset square hole 18 adapted to receive square bolt portion 19 ofbolt 20. Thus the bolt is passed through dowel' 16 and turned to revolveoffset cam 17 downward so as to urge the dowel down in tight fittingrelationship with recess 15. Recess 15 must be large enough in width togive dowel 16 enough sidewise or lateral play during the camming actionof the bolt. The bolt is then secured by nut 21 to effect a rigidstructure.

The curved segments may be made from a molding mixture or from a plasticcomposition. Each layer of curved building elements forming the igloomay be made from equal sized elements. For example, lookingat the topview of Fig. 2, it will be noted that the curved segments forming eachlayer are of equal size being cut in 60 sectors. Referring to Fig. 4,element 13 being all the same size and divisible into 360 would fittogether to form a circular wall. Likewise, element 14 would similarlyfit together. Since the elements in each layer would be the same size,then one mold would be required to make elements 13 and one mold to makeelements 14. A molding mixture would be poured into the mold and shapedto the mold contour and after the material has solidified, the formedelement is then removed.

Polar cap 5 would be made similarly in another mold.

The elements of the dome could all be made simultaneously in a flexiblecompartmented rubber mold such as described in my copending applicationU.S. Ser. No. 601,389, filed August 1, 1956. The entrance portion 2 ofthe igloo would be made in a separate mold. The entrance may be made asa unitary structure'or may comprise several pieces of two side wallportions supporting an archway portion. In making the entrance, the partcontacting the igloo, e.g. 2a, should coincide substantially with thecurvature of the dome. An opening would run through one of the buildingsegments at the base of the igloo where the entrance portion abuts it.This element with the opening would be produced in a separate moldsimilar to the production ofthe other elements.

The present invention is also adaptable to three-dimen- In thisconnection, the invention can be adapted to the making of a world reliefmap in the form of a hemispherical globe. is desired showing reliefs ofwindows, doors and the like, the interior mold surface can be reliefedwith such surface configurations. Even three dimensional picture puzzlescan be made in the same way, that is with the pictures imprinted bymolding on the curved surface of the dome. Such puzzles would have aconsiderable educational value for children.

Or, if a dome-like building While the present invention has beendescribed with respect to a toy igloo, it will be appreciated that theinventive concept is also applicable to the production of largeinhabitable dome-like structures.

While the present invention has been described in conjunction withpreferred embodiments, it is to be understood that modifications andvariations may be resorted to without departing from the spirit andscope of the in-- vention, as those skilled in the art will readilyunderstand. Such modifications and variations are considered to bewithin the purview and scope of the invention and a plane substantiallyparallel to each other, each of said planes passing transversely throughand substantially perpendicular to the polar axis of said dome-likestructure produced from said segments, each segment also having fiatside edges transverse to said curved surfaces and which lie in radialplanes which contain the polar axis of said dome-like structure producedtherefrom, the thickness of each of said three-dimensionally curvedsegments varying as a curved taper in the upwardly direction by virtueof the inner and outer curved surfaces converging towards each other,the curved taper being such that in radial cross section the center ofgravity of each segment is to one side of an inner fulcrum supportingedge and Well within the segment towards the outer surface thereof, therelation of the curved taper of an underlying segment with that of oneor more segments superposed thereabove being such that taken as a wholethe superposed segments including the underlying segment forming thebase of the structure have a combined center of gravity well within theradial cross section of the segments combined whereby they have uprightstability relative to the surface supporting the dome-like structureformed from all of the segments.

2. The set of building blocks as defined in claim 1 wherein the threedimensionally curved segments have fitting means adapted to connect oneblock to the other to form a rigid structure.

3. A dismantable toy igloo of a hollow dome-like configurationcomprising apolar cap on top of a stacked arrangement of a plurality ofthree-dimensionally curved segments characterized by upright stability,a group of said segments forming a first row constituting the base ofsaid igloo, another group of said segments forming at least one rowsuperposed on top of the first row, each of said building segmentshaving inner and outer curved surfaces and having a pair of flat surfaceportions transverse to said curved surfaces each lying in a planesubstantially parallel to each other, each of said planes pass ingtransversely through and substantially perpendicular to the polar axisof said igloo, each segment also having fiat side edges transverse tosaid curved surfaces and which lie in radial planes which contain thepolar axis of said igloo produced therefrom, the thickness of each ofsaid three-dimensionally curved segments varying as a curved taper inthe upwardly direction by virtue of the inner and outer curved surfacesconverging towards each other, the curved taper being such that inradial cross section the center of gravity of each segment is to oneside of an inner fulcrum supporting edge and well within the segmenttowards the outer surface thereof, the relation of the curved taper ofan underlying segment with that of one or more segments superposedthereabove being such that taken as a whole the superposed segmentsincluding the underlying segment forming the base of the structure havea combined center of gravity well within the radial cross section of thesegments combined whereby they have upright stability relative to thesurface supporting the igloo. I

4. The igloo of claim 3 wherein the three-dimensionally curvcd segmentshave fitting means adapted to connect one block to the other to form arigid structure.

5. The igloo of claim 3 wherein at least one of the 10 segments formingat the base thereof has passageway means associated therewith.

6 References Cited in the file of this patent UNITED STATES PATENTS1,124,078 Vershofen Jan. 5, 1915 1,467,340 Siegel Sept. 11, 1923 FOREIGNPATENTS 111,763 Great Britain Dec. 13, 1917 812,534 Germany Sept. 3,1951 459,123. Italy Aug. 25, 1950 OTHER REFERENCES Popular Mechanics, p.157, March 1951.

